(1) Field of the Invention
The present invention relates to a parts aligner for use in aligning a large number of randomly stored parts each in a unified posture and is suitable, in particular, in automatically feeding welding nuts as parts to automatic welding equipment with each in a prescribed posture.
(2) Description of Related Art
Conventionally, as a parts aligner of this kind, there has been known one in which vibration-rotation is applied to a bowl stored with parts to give a centrifugal force to the parts in the bowl, so that the parts move upward on a spiral slope located on the inner periphery of the bowl and undergo automatic posture shift, sorting by size and sorting by orientation (top or bottom) in the course of their upward movement.
Another parts aligner of this kind is disclosed in Japanese Patent Number 3117662. This part aligner comprises a face plate, a plurality of attraction means that are disposed to either one side (i.e., the front or back) of the face plate and move orbitally, and a posture shift guide and a top-bottom sorting means both disposed on the other side (the back or front) of the face plate. In this parts aligner, a part is attracted to the other side of the face plate by: the attraction means, and the attracted part is moved to the posture shift guide by an orbital movement of the attraction means so as to be shifted into a prescribed posture. Then, the part is moved to the top-bottom sorting means by a further orbital movement of the attraction means. This top-bottom sorting means removes a part whose top and bottom are not in a prescribed orientation by utilizing its difference in projection height from the face plate depending on the orientation of the top and bottom of the part. Thus, the parts aligner successively aligns parts as unified in the prescribed posture with the top and bottom of each put in the prescribed orientation.
The above parts aligner can align parts with each in the same orientation as long as the parts are of regular shape. However, for example, irregular parts that are totally thinner than the regular parts will pass through the top-bottom sorting means independently of whether the part face opposed to the face plate is the bottom or the top. The reason for this is that the top-bottom sorting means identifies the orientation of each part (i.e., whether the part is face-up or face-down) based on the projection height of a specific section (middle section) of each part from the face plate. Thus, irregular parts are often improperly mixed into regular parts.